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OSC Ha stacking and processing

edjrgibbs

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steppenwolf

steppenwolf

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I didnt think you could have Ha data from a OSC camera. But coul be wrong

Surprisingly, you can! The results don't match those of a mono CCD camera but back in 2007 I experimented with this using my OSC camera and was pleasantly surprised at how relatively well it worked:-

pelican_and_na_nebula_small_1.jpg

With regard to processing, stack as per a normal image, import into PS and convert to a greyscale image. Start gentle stretching using Curves and Levels.

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lensman57

lensman57

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Hi

Does anyone have a step by step guide to stacking in DSS then processing (i'll be using CS4) Ha data from a OSC camera (QHY8L)?

Thanks

Ed

Not only it is possible to obtain Ha or Oiii data from an OSC but it works surprisingly well though it could need very long exposures. I have no idea how DSS would do it as I use Pixinsight but I can tell you how it works. With an OSC sensor and an Ha filter only the RED pixels of the sensor ( due to the bayer array) will recieve the data and the Ha will filter out the blue and green light. So as the data is only contained in the RED channel the other two will only contribute unwanted noise and you really do not want this. The trick is to use Calibration Only and Pixel Debayering. Using this the subs will be calibrated but Super Pixel deBayer will not try to guess the missing data from the noisy blue and green Channels. The calibrated subs will then have the their Red channel extracted the debayered subs with the other two disposed of and then  these RED channel subs registered and then combined to give you a master Ha sub that will be mono. I think that DSS will probably have a similar routine as there is a SuperPixel Debayer option available and you just need to find a way of doing the rest of the routine. Hope helps a bit.

Here is a link to my latest Ha image from a Canon Modded 1100d. BTW your camera must modded for AP otherwise  it will not work.http://stargazerslounge.com/topic/227133-ic-5068-dslr-ha/

Regards,

A.G

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steppenwolf

steppenwolf

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MaxIm DL has an interesting colour conversion option called 'Extract Bayer Plane' which is designed specifically for this purpose. I wish I had known what this option did back in 2007!! Back then, I binned the image 2 x 2 to destroy the Bayer Matrix or simply converted to greyscale when I captured Ha data with my OSC CCD camera ......

Here is an extract from the Cyanogen Website:-

Occasionally you may want an image of only a single element of the Bayer matrix.  For example, when shooting through a hydrogen-alpha filter, all but the red pixels can be discarded. This command displays a simple dialog allowing you to select an element of a 2x2 matrix, and extract only those pixels from the original image in the chosen position. The result is an image one half the size of the original in each dimension.

Interesting stuff for those who want to experiment with narrowband and an OSC CCD camera or DSLR camera.

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lensman57

lensman57

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Ooops... 3 x 10 minutes Ha subs on the QHY8L before the clouds ended play. I'm actually quite happy with it.  Now just need to work out how to integrate the RGB tiff with the Ha tiff...

If you are using photoshop then it is easy. Open both files, split the channels of the RGB image and use the Ha as the red channel then recombine. You can also use a small percentage of the Ha as LUM to enhance sharpness, I think you just paste it on top of the RGB image with blending mode set  luminance and adjust the opacity to get the desired effect. Others maybe able to correct me if am wrong as I don't use PS for processing very much.

A.G

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ollypenrice

ollypenrice

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If you are using photoshop then it is easy. Open both files, split the channels of the RGB image and use the Ha as the red channel then recombine. You can also use a small percentage of the Ha as LUM to enhance sharpness, I think you just paste it on top of the RGB image with blending mode set  luminance and adjust the opacity to get the desired effect. Others maybe able to correct me if am wrong as I don't use PS for processing very much.

A.G

The problem with this, AG, is that the stars in Ha are much smaller so the red stars will lose a lot of their red and the outer parts will have too much blue and green. I'd suggest splitting the RGB channels and pasting the Ha onto red. Set that layer to blend mode lighten so that only where the Ha is brighter than the red will it be applied. This also allows you to stretch the Ha a little past its noise limit because the Ha background will probably remain well below the red background and it won't be applied. You can give the Ha layer a shove in Curves while it is on top if it doesn't seem to be doing much.

Olly

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steppenwolf

steppenwolf

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I'd suggest splitting the RGB channels and pasting the Ha onto red. Set that layer to blend mode lighten so that only where the Ha is brighter than the red will it be applied.

I use this method too although I prefer to do it iteratively with just a percentage of Ha followed by using a percentage of Ha as the Luminance channel (Ha as top layer, mode set to luminosity). I then flatten the image and repeat the exercise with an increased Ha content. I do several iterations of this to gently build up the Ha/red combination.

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lensman57

lensman57

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The problem with this, AG, is that the stars in Ha are much smaller so the red stars will lose a lot of their red and the outer parts will have too much blue and green. I'd suggest splitting the RGB channels and pasting the Ha onto red. Set that layer to blend mode lighten so that only where the Ha is brighter than the red will it be applied. This also allows you to stretch the Ha a little past its noise limit because the Ha background will probably remain well below the red background and it won't be applied. You can give the Ha layer a shove in Curves while it is on top if it doesn't seem to be doing much.

Olly

Sorry Olly I did not make myself clear, you are quite right. The Ha needs to be pasted on top of the R channel otherwise the star colours will be interesting.

Regards,

A.G

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ollypenrice

ollypenrice

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I use this method too although I prefer to do it iteratively with just a percentage of Ha followed by using a percentage of Ha as the Luminance channel (Ha as top layer, mode set to luminosity). I then flatten the image and repeat the exercise with an increased Ha content. I do several iterations of this to gently build up the Ha/red combination.

Yes, I used to do this but then I found a lazier way! (That's me all over... :grin: ) I tend to whack in the full monty of Ha onto red in blend mode lighten, flatten and save. I then paste this HaRGB on top of the pre-Ha version and select the opacity I like. I don't think it makes any difference and gives completely variable control of the Ha input.

Olly

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